The document provides information on the anatomy, physiology, and pathologic conditions of the spleen. It discusses the spleen's development, location, vasculature, and functions including filtering blood and immune roles. Secondary hypersplenism is defined as being caused by an underlying disease like disorders of splenic blood flow, hematopoietic disorders, immune disorders, infiltrative disorders, infections, or neoplasms. Specific conditions discussed in detail include hereditary spherocytosis, idiopathic thrombocytopenic purpura, myeloid metaplasia, and splenic abscess.

1. CHAPTER 22
SPLEEN
Canas Genevieve

2. Introduction
Anatomy
1. Developmental considerations
– The spleen develops from mesenchymal tissue in
the dorsal mesogastrium.
– This tissue rotates to the left as development
progresses.
– By the end of the third gestational month, the
organ is formed. The point at which the spleen
remains attached to the dorsal mesogastrium
becomes the gastrosplenic ligament.

4. – The organ itself consists of an outer capsule and
trabeculae, which enclose the pulp. The pulp consists
of three zones:
• The white pulp is essentially a lymph node. It contains
lymphocytes, macrophages, and plasma cells in a reticular
network.
• The red pulp consists of cords of reticular cells with sinuses
in between.
• The marginal zone is a poorly defined vascular space
between the pulps.
– The adult spleen weighs between 100 g and 150 g and
measures 12 — 7 — 4 cm.

5. 2. Location. The spleen is located in the left upper quadrant of
the abdomen and is protected by the eighth to the
eleventh ribs. It is bordered by the left kidney posteriorly,
the diaphragm superiorly, and the fundus of the stomach
and the splenic flexure of the colon anteriorly.
3. Vasculature
– The main blood supply is the splenic artery, which is a branch of
the celiac axis. It travels along the superior border of the
pancreas. At the hilus, it branches into trabecular arteries, which
terminate in small vessels to the splenic pulp.
– The splenic vein crosses behind or at the lower border of the
pancreas. It joins the superior mesenteric vein to form the
portal vein

6. Physiology
• The spleen has multiple functions, some of
which remain poorly understood. Its most
important functions are its ability to act as a
blood filter and its role in the immunologic
process of the body.
1. Filtering functions. Splenic blood flow is
approximately 350 L/day of blood. Most blood
elements pass through rapidly and
uneventfully.

7. a. Removal of old or abnormal red blood cells
• The spleen removes about 20 mL/day of aged or abnormal
red blood cells.
• Cells that have immunoglobulin G (IgG) on their surfaces are
removed by monocytes in the spleen. This removal of cells
may be the mechanism of increased cell destruction in some
diseases, such as idiopathic thrombocytopenic purpura and
autoimmune hemolytic anemia.
b. Removal of abnormal white blood cells, normal and
abnormal platelets, and cellular debris

8. 2. Immunologic functions
– Opsonin production. The entire
reticuloendothelial system is capable of removing
well-opsonized bacteria from the circulation, but
the spleen, with its highly efficient filtering
mechanism, is particularly suited to removing
poorly opsonized or encapsulated pathogens.

9. – Antibody synthesis. This synthesis occurs mainly in the
white pulp, where soluble antigens stimulate the
production of immunoglobulin M (IgM).
– Protection from infection. It is well established that
splenectomy leaves some patients more susceptible
to infection.
3. Storage functions. Approximately one third of the
body's platelets are stored in the spleen. In some
pathologic states, the percentage is increased.

10. Hypersplenism
• Hypersplenism refers to the exaggerated
destruction or sequestration of circulating red
blood cells, white blood cells, or platelets by
the spleen. The term should not be confused
with splenomegaly, which refers only to
physical enlargement of the spleen.
A . Primary hypersplenism is uncommon.

11. B. Secondary hypersplenism is caused by an
identifiable underlying disease, such as:
• Disorders of splenic blood flow
• Hematopoietic disorders leading to increased red
blood cell turnover
• Immune disorders
• Infiltrative disorders
• Infectious diseases
• Neoplastic diseases

12. c. Presentation
1. Anemia, leukopenia, or thrombocytopenia may be
noted on a routine laboratory workup.
– Anemia may lead to pallor, fatigue, and dyspnea.
– Leukopenia may lead to increased susceptibility to
infection.
– Thrombocytopenia is characterized by easy bruising and
epistaxis.
2. Splenomegaly may be found incidentally during the
physical examination or in a radiologic imaging study.
3. The patient may present with pain secondary to splenic
enlargement or rupture.

13. D. Evaluation
1. Peripheral blood smears may demonstrate a decreased
number of red blood cells, white blood cells, or platelets.
– Reticulocytosis is frequently observed if the hypersplenism is
causing an increased turnover of red blood cells.
– Abnormal red blood cell morphology is sometimes diagnostic
for the underlying hematologic disorder (e.g., spherocytosis).
2. Bone marrow aspirate
– A compensatory increase in megakaryocytes should be
observed if there is sequestration of platelets in the spleen.
– Abnormalities of hematopoiesis may be identified as well.

14. 3. Radiologic imaging
– An ultrasound or a computed tomography (CT) scan
can accurately document the size of the spleen as well
as determine any structural abnormalities.
– Radioisotope scans may demonstrate a shortened
half-life for circulating blood elements and their
sequestration in the spleen.
4. Immunologic tests using specific antibodies may
be diagnostic for certain diseases, particularly
those with an autoimmune basis.

15. Pathologic Conditions Affecting the
Spleen
A. Primary splenic disorders
Primary hypersplenism is essentially a
diagnosis of exclusion; it is made only after
possible causes of secondary hypersplenism
have been ruled out.

16. – It is rare, and it affects mainly women.
– There is an exaggerated destruction or sequestration of
circulating blood elements.
• Any one or all of the formed blood elements may be involved.
• The hematologic findings may be accompanied by recurrent fevers
and infections.
– Splenomegaly is almost always present.
– It may, in some cases, actually be an early manifestation of
lymphoma or leukemia.
– The treatment is splenectomy. Steroids do not improve the
condition.

17. 2. Splenic cysts may be idiopathic or, more
commonly, may result from previous trauma.
Surgery is indicated if the cysts become large
enough to cause pain or torsion or if they
exert a significant mass effect on surrounding
structures.

18. B. Disorders of splenic blood flow
1. Portal hypertension may cause passive splenic
congestion.
– It is the most common mechanism of secondary
hypersplenism.
– Causes of portal hypertension include alcoholic
cirrhosis, viral hepatitis, Budd-Chiari syndrome, and
congestive heart failure.
– Hypersplenism associated with portal hypertension is
usually mild and clinically insignificant. Only 15% of
patients develop significant hypersplenism; therefore,
isolated splenectomy is generally not indicated.

19. 2. Splenic vein thrombosis can cause secondary
hypersplenism with massive splenomegaly.
– Cause. Pancreatitis is the usual cause of the
thrombosis.
– Presentation. The patient may present with
bleeding from esophageal or, more
characteristically, proximal gastric varices.
– Treatment. The hypersplenism and bleeding
varices are cured by splenectomy.
3. Splenic artery aneurysm

20. C. Hematopoietic disorders
1. Hereditary spherocytosis is one of a group of
hereditary hemolytic anemias that cause the
most severe symptoms.
a. Characteristics
• Hereditary spherocytosis is characterized by a defect of the
red blood cell membrane that results in loss of red blood cell
surface area, which causes the cell to be spherical ,small,
and more susceptible to lysis than normal red blood cells.
• The cell membrane is thick and rigid, which causes the cells
to be held in the splenic pulp.
• It is transmitted as an autosomal dominant trait.

21. b. Symptoms
• Symptoms of hereditary spherocytosis include malaise,
abdominal discomfort, jaundice, anemia, and
splenomegaly.
• The disease may be complicated by gallstones (which
are rare in patients younger than 10 years of age) and
by chronic leg ulcers that heal only after splenectomy.

22. c. Diagnosis is based on the preceding clinical
findings and the results of laboratory studies,
which include a demonstration of the following:
• Spherocytes and an elevated reticulocyte count on a
Wright-stained blood smear
• Increased osmotic fragility of the red blood cells
• Chromium 51 (51Cr)-tagged red blood cells, which have
a greatly shortened half-life and are sequestered in the
spleen

23. d. Treatment is splenectomy.
• This procedure cures the anemia and jaundice in all
patients. Failure of splenectomy to cure the patient is
normally caused by an accessory spleen that has been
overlooked during the operation.
• The operation should be delayed until 4 years of age, if
possible, to decrease the chance of postsplenectomy
sepsis
• The gallbladder should be removed at the time of
splenectomy if gallstones are present.

24. 2. Other congenital hemolytic anemias
– Enzyme deficiencies, such as glucose-6-phosphate
dehydrogenase (G6PD) deficiency and pyruvate kinase
deficiency
– Hereditary elliptocytosis, in which most of the
patient's erythrocytes are misshapen (i.e., they are
elliptical) and there are varying degrees of anemia and
red blood cell destruction
– Thalassemia major, which is transmitted as a
dominant trait and is characterized by defective
hemoglobin synthesis that causes homozygotes to
have severe anemia and hepatosplenomegaly

25. • 3. Sickle cell anemia
– Most patients with sickle cell anemia
autosplenectomize because of multiple infarcts
caused by stagnation and stasis of the abnormal
red blood cells.
– These patients may require splenectomy in rare
cases in which excessive splenic sequestration of
red blood cells is documented or when areas of
infarction develop an abscess.

26. 4. Congenital erythropoietic porphyria is a rare
autosomal recessive defect of pyrrole
metabolism that leads to deposition of
porphyrins in the skin and other tissues.
– Patients have photosensitivity, bullous dermatitis,
and hemolytic anemia.
– Splenectomy improves the hemolytic anemia and
decreases tissue levels of porphyrins.

27. D. Immune disorders
1. Idiopathic autoimmune hemolytic anemia
occurs most commonly in persons older than
50 years of age and occurs twice as often in
women than in men.
a. Clinical presentation
• In this disorder, both warm and cold hemolytic
antibodies have been described. These antibodies
presumably shorten the life of the red blood cells.
• The anemia is accompanied by reticulocytosis. There is
splenomegaly in 50% of the patients, and there may be
mild jaundice.

28. 2. Diagnosis. The direct Coombs' test result is
positive. 51Cr-tagged red blood cells may
demonstrate sequestration in the spleen.
3. Treatment. The disease may run a self-limited
course that requires no treatment.
• Steroids and azathioprine are administered in more
persistent cases.
• Splenectomy is helpful in some patients, especially if
they have demonstrated excessive splenic
sequestration of 51Cr-tagged red blood cells, and if
steroids are ineffective or contraindicated.

29. 2. Idiopathic thrombocytopenic purpura (ITP)
a. The etiology is unknown but is presumed to be
immunologic because most patients with chronic
disease have platelet-agglutinating antibodies that
rapidly destroy transfused platelets.
• The acute form is more common in children younger
than 16 years.
• The chronic form is most common in adults, and
women predominate in a ratio of 3:1.

30. b. Clinical presentation
• This disease is characterized by a decreased platelet count
accompanied by increased megakaryocytes in the bone
marrow. The spleen is usually not enlarged.
• The disease presents as unexplained ecchymoses or
petechiae, often accompanied by bleeding from the gums or
hematuria.
c. Treatment
• Steroids induce remission in 75% of patients; approximately
20% of these patients have a sustained response.
• Splenectomy is commonly indicated in individuals who do
not respond to steroids or in those who have a relapse after
steroids are tapered off. It is also indicated if central nervous
system bleeding occurs.

31. 3. Thrombotic thrombocytopenic purpura (TTP) is a
rapidly progressive and usually fatal disease. It is
also thought to have an immunologic basis.
a. Clinical presentation includes fever,
thrombocytopenic purpura, hemolytic anemia,
neurologic disturbances, and renal failure.
b. Diagnosis is confirmed only by biopsy of a purpuric
lesion. This characteristic vascular lesion consists of
occlusion of arterioles and capillaries by a hyaline
membrane.

32. c. Treatment. The most effective treatments are
splenectomy and steroid therapy. Plasmapheresis,
antiplatelet agents (e.g., dextran), or exchange
transfusions with fresh blood have resulted in
survival in a few patients.
d. Prognosis. The long-term survival rate is less than
10%, even with optimal therapy.

33. 4. Felty's syndrome
a. Clinical presentation
• Felty's syndrome is a triad consisting of chronic
rheumatoid arthritis, splenomegaly, and
granulocytopenia.
• Spontaneous serious infections can occur due to
neutropenia, and splenectomy is helpful in this group
of patients.
b. Treatment. Splenectomy may also be indicated for
management of intractable leg ulcers, severe
thrombocytopenia, and anemia.

34. E. Infiltrative diseases
1. Myeloid metaplasia is thought to be related to
polycythemia vera and myelogenous
leukemia.
a. Clinical presentation
• It is characterized by connective tissue proliferation in
the bone marrow, liver, spleen, and lymph nodes and is
accompanied by proliferation of the hematopoietic
tissue of the liver, spleen, and long bones.
• The usual symptoms are anemia and splenomegaly,
which usually appear in middle-aged or older adults.
Secondary hypersplenism may develop.

35. b. Treatment
• Primary treatment consists of alkylating agents to
reduce the size of the spleen and male hormones to
stimulate failing bone marrow and to treat anemia.
• Splenectomy does not change the course of the
disease, but it may help to control the hypersplenism.

36. 2. Sarcoidosis
– Patients typically have diffuse lymphadenopathy,
skin lesions, and pulmonary abnormalities.
Approximately 25% of patients develop
hypersplenism.
– There is no specific treatment, but patients with
significant hypersplenism may experience
resolution of their hematologic abnormalities
after splenectomy.

37. 3. Gaucher's disease is an inborn error of
metabolism characterized by deposition of
glucosylceramide lipids throughout the
reticuloendothelial system, which causes
hepatosplenomegaly and bone pain.
– Significant hypersplenism is an indication for
splenectomy.
– Because the diagnosis is often made in childhood,
partial splenectomy may be indicated to preserve
some immunologic function.

38. F. Infectious diseases
• may cause splenomegaly and hypersplenism.
Treatment is generally medical, although
surgery may be indicated for abscess or
disease localized to the spleen.
1. Bacterial infections may cause abscess
formation or transient splenic enlargement.
Splenic abscess is uncommon but has a high
mortality rate when it occurs.

39. a. Causes include the following:
• Infection of a pre-existing lesion, such as a hematoma
or an infarct
• Direct spread from adjacent structures, such as the
pancreas or colon
• Hematogenous seeding from a remote size (especially
in users of intravenous drugs) or during overwhelming
bacteremia (e.g., in endocarditis)
• Most common organisms causing infection are
Staphylococcus aureus or streptococcus. Less common
pathogens include Salmonella or anarobes.

40. b. Diagnosis should be suspected if signs of abscess,
such as fever and an elevated white blood cell
count, occur in association with left upper
quadrant fullness or tenderness. It can be
confirmed by CT scan and scanning with
technetium-99m
b. Treatment is broad spectrum antibiotics and
splenectomy. Percutaneous drainage may be
considered in select cases, but hemorrhage is a
potential complication.

41. 2. Viral infections including mononucleosis, human
immunodeficiency virus, and hepatitis may cause
transient splenomegaly and hypersplenism.
3. Parasitic infections including malaria,
leishmaniasis, or trypanosomiasis affect blood
cells and may cause splenomegaly. An
echinococcal cyst may develop in the spleen.
Partial or total splenectomy is curative.
4. Fungal infection with histoplasmosis produces
characteristic areas of calcification within the
spleen.

42. G. Neoplastic diseases
1. Primary splenic tumors are rare.
– They include lymphoma, sarcoma, hemangioma,
and hamartoma.
– Symptoms are caused by the enlarged spleen, and
there may be associated hypersplenism.
– Treatment is splenectomy.

43. 2. Metastatic disease from solid tumors is
uncommon, probably owing to its efficient
immune mechanism.
3. Hodgkin's disease. Treatment may include
radiation therapy alone, chemotherapy alone,
or a combination of both.

44. a. Types of staging
b. Staging laparotomy consists of liver biopsy,
splenectomy, complete abdominal exploration, and
sampling of lymph nodes from multiple areas but is
now performed only rarely.
c. Laparotomy is clearly not indicated in patients with
stage IIIB or IV disease. Chemotherapy is the
treatment of choice.

45. 4. Non-Hodgkin's lymphoma
– Staging for non-Hodgkin's lymphoma uses the same
classification as for Hodgkin's disease. Careful
evaluation reveals stage III or IV disease in most
patients.
– Laparotomy is not frequently used in non-Hodgkin's
lymphoma. Percutaneous liver biopsy, laparoscopy, or
bone marrow biopsy frequently reveals diffuse
disease.
– Splenectomy may be useful in some of these patients
to treat hypersplenism or to relieve symptoms of
massive splenomegaly.

46. 5. Leukemias
– Patients with chronic lymphocytic leukemia (CLL)
or chronic myelogenous leukemia (CML) may
develop thrombocytopenia and massive
splenomegaly. Splenectomy is indicated for
symptomatic relief.
– Patients with hairy cell leukemia and
hypersplenism may benefit from splenectomy.

47. H. Miscellaneous lesions
1. Rupture of the spleen may follow either
penetrating or nonpenetrating trauma as well as
iatrogenic injury, or rupture may occur
spontaneously.
a. Traumatic rupture
b. Iatrogenic (intraoperative) trauma accounts for 20%
of all splenectomies. The trauma results from
excessive traction on the splenic attachments or from
misplacement of retractors.
c. sSpontaneous rupture usually occurs because of
massive splenomegaly due to an associated disease.

48. 2. Splenosis is autotransplantation of splenic
fragments throughout the abdominal cavity.
3. Aneurysms of the splenic artery
4. Ectopic and accessory spleens
– An ectopic spleen is caused by a long splenic pedicle,
which allows the spleen to wander about the
abdomen.
– Accessory spleens are found in approximately 10% of
autopsies. These spleens are usually located near the
hilus or the tail of the pancreas and less frequently in
the mesentery.

49. Complications after Splenectomy
A . Atelectasis of the left lower lung is the most
common complication.
B. Injury to surrounding structures
a. The gastric wall may be injured in the course of
controlling the short gastric vessels. In extreme
cases, this injury may lead to necrosis of the
gastric wall with delayed perforation.
b. The tail of the pancreas may be injured during
attempts to secure hemostasis of the splenic
pedicle.

50. C. Postoperative hemorrhage may result from
inadequate hemostasis of the splenic pedicle
or the short gastric vessels.
D. Subphrenic abscess may develop and is
usually accompanied by a left pleural effusion.
E. Thrombocytosis postoperatively is common.

51. F. Postsplenectomy sepsis
1. The syndrome begins with nonspecific, mild, influenza like
symptoms and progresses to high fever, shock, and death.
– In general, the younger the patient and the more serious the
disease requiring the splenectomy, the greater is the risk for the
development of overwhelming sepsis.
– In healthy adults who have the spleen removed for trauma, the
incidence of overwhelming sepsis is low (<0.5%), but it is still
higher than that in the normal population (0.01%).
– Approximately 80% of septic episodes occur within 2 years after
splenectomy.
– Typically, the causitive organisms are encapsulated bacteria,
including Streptococcus pneumoniae, Neisseria meningitidis,
and Haemophilus influenzae.

52. 2. Prevention and treatment
– Polyvalent pneumococcal vaccine should be given
to all splenectomized patients, which will protect
them from 80% of pathogenic pneumococci (the
organisms that most commonly cause the sepsis).
– Vaccines for N. meningitidis and H. influenzae
should be administered as well.
– Prophylactic penicillin may be given to high-risk
pediatric patients.

53. Critical Points
1. The spleen is an important but not essential organ that
has a role in filtering and sequestering circulating blood
elements.
2. The spleen has an important immunologic role,
filtering opsonized bacteria from the circulation and
providing a site for antibody synthesis.
3. Hypersplenism should not be confused
withsplenomegaly.
– Hypersplenism refers to the exaggerated destruction of
sequestration of circulating red blood cells, white blood
cells, or platelets.
– Splenomegaly refers to physical enlargement of the spleen
only.

54. 4. Primary hypersplenism is uncommon and is a
diagnosis of exclusion, occurring mostly in
women.
5. Most cases of hypersplenism are secondary to
other pathologic conditions.
– Disorders of splenic blood flow, including portal
hypertension or splenic vein thrombosis
– Hematopoietic disorders, including hereditary
spherocytosis, hemolytic anemias, sickle cell
disease, or congenital erythropoietic porphyria

55. 6. Immunologic disorders, including idiopathic
autoimmune hemolytic anemia, ITP, TTP, or Felty's
syndrome.
• ITP is one of the most common reasons for elective
splenectomy. In this condition, the spleen is generally
normal in size.
7. Infiltrative diseases, including myeloid metaplasia,
sarcoidosis, or Gaucher's disease
– Infection diseases, including bacterial, viral, parasitic,
or fungal infections
• S. aureus and streptococci are the most common etiologic
agents.

56. 8. Traumatic rupture of the spleen can often be managed
nonoperatively. Splenectomy is reserved for those
patients who are unstable or who have additional,
massive injuries.
9. The management of most cases of hypersplenism is
medical. Splenectomy usually has only a secondary
role, when symptoms are significant or medical
therapy fails to control the disease.
– The conditions where surgery is clearly indicated are
bleeding esophagogastric varices associated with splenic
vein thrombosis, hereditary spherocytosis, splenic abscess,
echinococcal cyst, primary splenic tumors, massive splenic
trauma, or spontaneous rupture

57. 10. Neoplastic diseases of the spleen are uncommon
but may include primary tumors, metastatic tumors,
or hematologic disorders such as lymphoma.
11. Surgery is frequently performed through a
laparotomy incision but may also be performed
laparoscopically.

58. 12. Patients undergoing splenectomy are at risk
for developing overwhelming
postsplenectomy sepsis. This risk is greatest in
young children. The risk can be decreased by
prophylactically immunizing patients
preoperatively or postoperatively, if necessary.